Commander McLane & Charlie
Thanks for the info about quaternions!
I've been trying to write out a simple spreadsheet that would combine any two quaternions from that table that you linked to charlie using the formulas from Commander McLane's post and display the result, it seems to be working with the 180degree stuff but i'm not sure what values i should be typing in for the 90degree stuff, the table just puts "sqrt(0.5)", should i type in 0.5 or the squareroot of 0.5 or what?
here's a screenshot of the spreadsheet
you just work out which two quaternions you need from the table, type them into the two red rows in the spreadsheet and you get the required quaternion in the yellow box - well, at least that's the plan.

Edit D'oh should have checked the wiki, i found a page that gave the formulas on how to generate quaternions around a single axis for any angle, i've added that into the spreadsheet so it should now be possible to generate single axis quaternions for any angle and axis and combine them in the multiplier.

Right, just to clarify what i've learned from building my Nuit station...
if you wanna do a new fancy-looking dock :-

- i used dock-flat.dat as a template for sizes : use your modeller to create a box of the same size/shape, and then delete the front face, ie the entrance. Then turn the goddamn thing inside out, or you won't be able to see it.this box has to be modelled at the origin, (0,0,0). This is the important bit that was doing my head in. for some reason Oolite seems not to recognise a displaced dock model - you have to create it where it expects it to be, and then tell it in the OXP that it has been moved :-/

- do the usual stuff, skinning, DAT converting etc. your ship/station model should obviously have a gap in its wall/hull the same size as the dock entrance.

- in your OXP shipdata plist, the dock will be included as a subentity of the ship/station. give it a name that includes the word "dock", and use the positioning variables to shift the model from the origin to its correct place; this may take a bit of trial and error.
eg:
" subentities = (
"dock-nuit -11.5 3004 421 1 0 0 0","

- the dict definition itself is straightforward. i gave mine the word "dock" in its role too.

Hah, wish I knew about this thread earlier, I learnt most of the stuff in this thread through trial and error, I had things like docks appearing inside out, facing weird directions, not working at all, upside down, etc.

what formats are supported (.png, .jpg, ...) and which is the preferred one?

PNG only.

Quote:

is there an optimal resolution? (from an error message I learned that length and height should be dividable, e.g. 1024*512)

As you already found out, all dimensions must be powers of two. So, for a rectangular picture, you could also use 512*256 or 256*128. For a square picture, you should be fine with 512*512 or 256*256.

Quote:

any other things to keep in mind?

At least as far as texture PNGs are concerned, they must not be saved in interlaced mode. I don't know whether this is as strict a requirement for background images, but it certainly doesn't hurt to save them non-interlaced.